1. Field
Embodiments of the present invention relate to a pixel and an organic light emitting display device including the same.
2. Description of the Related Art
In recent years, various flat panel displays having reduced weight and volume in comparison to cathode ray tubes have been developed. Examples of the flat panel displays include liquid crystal displays, field emission displays, plasma display panels, organic light emitting display devices, etc.
An organic light emitting display device, which is one of the flat panel displays, displays images by using organic light emitting diodes that generate light by recombining electrons and holes, has rapid response speed, and is driven with low power consumption.
The organic light emitting display device includes a plurality of pixels that are arranged in a matrix pattern at crossing regions of a plurality of data lines, scan lines, and power supply lines. Each of the pixels generally includes an organic light emitting diode, two or more transistors including a driving transistor, and one or more capacitors.
Such an organic light emitting display device typically has low power consumption, but the amount of current that flows on the organic light emitting diode may vary depending on a threshold voltage variation of the driving transistor included in each of the pixels, thereby causing display nonuniformity. That is, characteristics of the driving transistor vary depending on variables of a manufacturing process of the driving transistor included in each of the pixels. Actually, it is very difficult or impossible to manufacture all transistors of the organic light emitting display device to have the same characteristic in a process step using existing technologies. As a result, threshold voltage variations of the driving transistors are generated.
In order to solve the problem, a method of adding a compensation circuit constituted by a plurality of transistors and capacitors in each of the pixels has been proposed. The compensation circuit included in each of the pixels charges voltage corresponding to threshold voltage of the driving transistor to thereby compensate for the threshold variation of the driving transistor.
Recently, a driving method using a frequency of 120 Hz or more has been used in order to remove a motion blur phenomenon. However, in the case of high-speed driving at 120 Hz or more, a charging duration of the threshold voltage of the driving transistor is shortened, such that compensation of the threshold voltage of the driving transistor may become very difficult or impossible. Further, in the high-speed driving at 120 Hz or more, an initialization period when a gate electrode of the driving transistor is initialized to a predetermined voltage cannot be sufficiently ensured before the threshold voltage is compensated, as a result, stable compensation is very difficult or impossible.